Who is Daniel Madison from Sister, Sister and what is their importance?

Daniel Madison lives near Valerie and jogs past her house fairly often because he has a crush on her. He is a clean-cut, pretty man around thirty years old with short stylish hair and light sideburns. He is 5'9", has caramel-colored skin and an agile, runner's build. Valerie dances with Daniel at the jazz club in San Bernardino, but after meeting him a few times, she breaks it off because she feels guilty since she is married. After Valerie separates from Walter, she begins seeing and sleeping with Daniel. Daniel treats Valerie very well, but they are just friends since he goes to graduate school in North Carolina; however, Valerie admits that they might get together if he comes back to California after graduation and they are both single.